1. Field of the Invention
The present invention relates to a method for controlling a neck detection for a welding power supply or source. More particularly, the present invention relates to a method for controlling a neck detection for a welding power supply wherein the neck detection can be suitably performed even if the welding power supply is combined with another power supply for performing a simultaneous arc welding operation at a plurality of locations of a workpiece. The present invention also relates to a welding power supply system having such a control function.
2. Description of the Related Art
In consumable electrode arc welding, formation of an arc and short-circuiting occur alternately between a welding wire and a workpiece. As a phenomenon that occurs before the formation of an arc, a neck is formed in a molten portion of the welding wire before forming a molten droplet. In a conventional method for controlling the output from an arc welding power supply, the formation of a neck is detected based on a change in voltage or resistance between the welding wire and the workpiece. Upon detecting the formation of a neck, the welding current applied to the short-circuiting load is rapidly reduced, so that an arc is formed under application of a low current. According to this control (neck detection control), generation of spatter is suppressed, since only a low current is applied at the time of arc formation. This type of control is disclosed in e.g. JP-A-2006-281219 (which issued as Japanese Patent No. 4907892) and JP-A-2012-240101A.
Welding is sometimes performed simultaneously at a plurality of locations of a single workpiece by using a plurality of welding power supplies. However, the neck detection control disclosed in either of the two Japanese documents deals only with the case where consumable electrode arc welding is performed only at a single location with a single power supply. Therefore, the neck detection control disclosed in the two Japanese documents is not suitable where a plurality of power supplies (i.e., two welders) are used for performing consumable electrode arc welding simultaneously at a plurality of locations of a workpiece, since the state of one power supply may be affected by the state of another power supply operating at the same time.